The crystal structure of α‐TiCl<sub>3</sub> and the reticular disorder introduced by ball‐milling

Gerbasi, R.; Marigo, Antonio; Martorana, Antonino; Zannetti, Roberto; Guidetti, G.; Cojazzi, Gianna

doi:10.1002/macp.1984.021850119

Cited by 8 publications

(3 citation statements)

References 18 publications

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“…The first major breakthrough in the Z-N catalysts in 1968 was promoted by Montedison (now LyondellBasell) and Mitsui with the discovery of the milled MgCl 2 support for ethylene polymerization [17][18][19]. This technology was adopted by the extra addition of internal and external electron donors to improve the isotacticity of PP without catalyst activity in the PP industry in the 1970s, which led to the third-generation of PP catalysts, eliminating the need for catalyst residue removal, but the atactic content was still too high.…”

Section: Introductionmentioning

confidence: 99%

Versatile Polypropylene Copolymers from a Pilot-Scale Spheripol II Process

Wang

Kang

et al. 2020

Polymers

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Polypropylene (PP) is one of the most widely used polymers. In this paper, three types of PPs including random PP, impact PP, and impact PP with high clarity, were prepared through a 75 kg/h pilot-scale Spheripol II process. The three produced PPs were produced by the selection or combination the two loops and gas phase reactor and controlling the comonomer and hydrogen concentrations. The three prepared PPs then were pelleted with the clarified nucleating agent NX 8000 and tested for mechanical, thermal, and optical properties. Their molecular structures and rubber phase size were also investigated by GPC, 13C NMR, temperature rising elution fractionation (TREF), XRD, SEM analysis, etc. The results showed that the random PP (PP-1) and the impact PP with high clarity (PP-3) obtained excellent optical transparency with a haze of 12.5% and 13.5% due to their small rubber phase size (roughly ≤ 100 nm), while the impact PP (PP-2) obtained bad transparency with a haze of 98.8% due to the large rubber phase size (about 1 μm) caused by the poor thermal compatibility with the PP matrix. The rubber phase content and ethylene/propylene sequence distributions of the three PPs varied much and resulted in different impact strengths and stiffness properties. PP-2 had a high impact strength of 14.5 kJ/m2 due to the rubber phase generated in the gas phase reactor. Except for the optical transparency, PP-3 gained stiffness and toughness, with 914 MPa of flexural modulus and 25.1 kJ/m2 of impact strength due to the unique molecular structure of its rubber phase.

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Section: Introductionmentioning

confidence: 99%

Versatile Polypropylene Copolymers from a Pilot-Scale Spheripol II Process

Wang

Kang

et al. 2020

Polymers

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“…Thus, the ball-milling of the Ziegler-Natta catalyst has been investigated (Gerbasi et al, 1984). Thus, the ball-milling of the Ziegler-Natta catalyst has been investigated (Gerbasi et al, 1984).…”

Section: Introductionmentioning

confidence: 99%

“…Another application of structure and texture determination of industrial compounds by X-ray simulation concerns catalysts. Thus, the ball-milling of the Ziegler-Natta catalyst has been investigated (Gerbasi et al, 1984). Very important work (Chien, Moss, Liang & Chianelli, 1986) was done on poorly crystalline MoS2, which is often used as a hydrotreating catalyst with nickel or cobalt promoter activity.…”

Section: Introductionmentioning

confidence: 99%

Powerful new software for the simulation of WAXS and SAXS diagrams

Espinat¹,

Thévenot²,

Grimoud³

et al. 1993

J Appl Cryst

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The study of poorly crystallized compounds by X‐ray powder diffraction is sometimes very difficult because structural information is not easily obtained. One way to determine these structural data is to test more or less complex crystallographic models and compare simulated wide‐angle X‐ray scattering (WAXS) and small‐angle X‐ray scattering (SAXS) spectra with experimental ones. This paper presents new software for the simulation of X‐ray patterns. Three modules are available; PRECRAY, SIMVAX and SIMVAX1. PRECRAY allows the definition of the structural model for the solid and different conditions for the calculation of the X‐ray diagram, such as the type of anode and the angular domain. SIMVAX and SIMVAX1 calculate all the interatomic distances according to the Debye formula; the contributions of the different kinds of atoms may be displayed. Applications to different sorts of material are presented; the influences of several kinds of crystallographic defects on the X‐ray diagrams have been studied. The relevance of this simulation approach to the interpretation of small‐angle X‐ray scattering patterns, by the generation of complex models of particles and calculation of the scattered intensity, is also presented.

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A new layer structure of VCL₃ showing stacking‐fault type disorder

Sam

Courtine

Jannel³

1985

Makromol. Chem., Rapid Commun.

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It is well known that the most stereospecific catalysts for the polymerization of a-olefins to isotactic polymers are the Ziegler-Natta heterogeneous catalysts. The most important component of these catalysts is a crystalline metal halide of the MtX, type characterized by a layer lattice (violet TiCl,, VCl,, etc.). In this communication, attention has been paid to the structural features of the active forms of some of these catalysts or even their supports.Ball-milling is quite a common procedure used to increase the activity of most solid catalysts. Generally, when a layer type structure catalyst undergoes ball-milling, the powder X-ray diffraction pattern of the ground catalyst exhibits considerable structural modification with respect to that of its starting material. This modification is observed with metal halides that can exist in at least 2 crystalline forms: a hexagonal close-packing and a cubic close-packing of the halogen atoms.Among the 3 crystalline forms, a-, /Iand y-TiCl,, in the best known Ziegler-Natta catalyst'), two of them, aand y-TiC1, are highly active in the polymerization of a-olefins. The violet forms aand y-TiC1, have a layer lattice structure and are triply layered with a metal layer between 2 chlorine layers. Only two thirds of the octahedral sites present are occupied by titanium atoms. The a-form consists of hexagonal closepacking of chlorine atoms, whereas a cubic close-packing of chlorine atoms is present in the y-form.When aor y-TiC1, is activated by grinding, a new violet modification is obtained.This new form, known as 6-TiC13, shows higher catalytic activity than its precursors. &-Tic!, has a triply layered structure and consists of both hexagonal close-packed and cubic close-packed chlorine atoms stacked randomly along the c crystallographic axis. This type of stacking may be called a polytypic disorder.The most active second generation Ziegler-Natta catalysts are those supported on MgCl,. The two crystalline forms of MgCl, (a and /I) are prepared chemically. The a-form, discovered long ago by Ferrari'), has a layer lattice with a cubic close-packing of chlorine atoms. Quite recently, a new form, B-MgCl,, having a hexagonal close-0173-2803/85/$01 .OO

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The crystal structure of α‐TiCl₃ and the reticular disorder introduced by ball‐milling

Cited by 8 publications

References 18 publications

Versatile Polypropylene Copolymers from a Pilot-Scale Spheripol II Process

Versatile Polypropylene Copolymers from a Pilot-Scale Spheripol II Process

Powerful new software for the simulation of WAXS and SAXS diagrams

A new layer structure of VCL₃ showing stacking‐fault type disorder

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The crystal structure of α‐TiCl3 and the reticular disorder introduced by ball‐milling

Cited by 8 publications

References 18 publications

Versatile Polypropylene Copolymers from a Pilot-Scale Spheripol II Process

Versatile Polypropylene Copolymers from a Pilot-Scale Spheripol II Process

Powerful new software for the simulation of WAXS and SAXS diagrams

A new layer structure of VCL3 showing stacking‐fault type disorder

Contact Info

Product

Resources

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The crystal structure of α‐TiCl₃ and the reticular disorder introduced by ball‐milling

A new layer structure of VCL₃ showing stacking‐fault type disorder